Suffolks have a particular problem with inbreeding as it has produced a defect in the breed, particularly in America. I can't remember any details at this time of night.
Sometimes 'line breeding' ie sire to daughter or dam to son, is carried out in order to perpetuate a specific desirable trait. Sibling in-breeding is not so usual. There is a difference between in-breeding and inter-breeding (cross-breeding).
I like your questions Andy, but there are not always black and white answers to them. In this case, in some instances in-breeding would be ok, but you must be aware that there can be problems. If you were only breeding for meat, then in-breeding would be less of a problem, but if you are producing breeding stock by in-breeding then you must be careful.
We breed breeding stock specifically so we do not in-breed unless we cannot help it. The Hebridean breed came through a tight bottleneck 130 years ago, so all individuals are already closely related, so we try to reduce the effect of that closeness by choosing tups which are as unrelated as possible (from their pedigrees). We run 5 or 6 Heb tups and 2 Soay tups, and I choose the mating groups very carefully to avoid consanguinity.
The first year, you use one tup. In Hebs we do not breed lambs, so that tup can be used for two years. In the third year we would get another tup to use on the daughters, and again the following year. After that another tup needs to be bought in, or offspring can be used on unrelated ewes. We could just change the tup every second year and use him over all the ewes, but it can be hard to find a perfect Heb tup with the characteristics we need,. so we use what we have for as long as possible, hence the 5 or 6 tups. For your Suffolks, which are a numerous breed, one possible answer would be to buy a tup lamb, use him for one season then put him in the freezer and buy another unrelated tup lamb the following year.
A problem with Suffolks is that there is a tendency to use AI from a small number of males or male lines - these are bought for huge sums, then this outlay is recouped by selling the semen. The effect of this is to produce the bottleneck we had in Hebrideans but artificially so making many Suffolks closely related. If any of these individuals carry recessive genes for a defect, which is not expressed, then mating them together will give the lamb a double copy of the defect which will then be expressed. If this is a significant defect then you have a problem, if it is not then you don't.
Topic: Please educate me, ram, ewe and lamb? (Read 7435 times)
